The present invention relates to a cathode structure of an electron gun for a cathode ray tube (CRT), and more particularly, to a cathode ray tube adopting a field emission device.
An indirectly heated or directly heated cathode is used as a thermion emission source in the CRT of existing monitors and televisions. Since the thermion emission material of the conventional cathode structure is heated by a special heating source to emit thermions, certain inherent problems arise. First, the period for emitting the normal thermions is relatively long since the thermion emission material is heated after support members for supporting the thermion emission material is heated with heat generated by the heating source. Accordingly, the time required to form a CRT image increases, for example, up to 8 or 9 seconds.
Second, a thermal drift phenomenon occurs due to the thermal expansion of the support member for supporting the thermion emission material.
Third, to heat the thermion emission material, power consumption of between 2 and 4 watts is required.
To overcome the above-mentioned problems, a cathode structure adopting a field emission device has been devised. Referring to FIG. 1, the cathode structure is comprised of an electrode member 11, an insulating member 12 combined with the electrode member, and a cell 20 installed on the insulating member and having field emission devices.
As shown in FIGS. 2 and 3, the cell 20 comprises a substrate 21 and three cathode layers 22 formed in a predetermined pattern on the substrate 21. A plurality of metal tips 23 for emitting electron beams corresponding to red, green, and blue signals are formed on the cathode layer 22. Each of the metal tips 23 is isolated from each other by an insulating layer 24 having openings 24a, and a gate electrode layer 25, having gates 25a through which the metal tips 23 are exposed, is formed on top of the insulating layer 24.
In the operation of the conventional cathode structure as constituted above, the amount of electrons emitted from the metal tips 23 is controlled by applying negative or zero voltages to the cathode layer 22 and a positive voltage to the gate electrode layer 25. Since the gate electrode layer 25 is formed on the overall surfaces of the substrate 21, the driving signal is distorted by the capacitance between the gate electrode layer 25 and cathode layer 22.